Preparing the 2nd lam — port chine, Zip

With the first lamination down, and a new order of epoxy on its way from Glen-L (I'm completely out), I started preparing the second lamination.

This basically involves 3 steps:

1. Cutting one end to fit at the stem
2. Planning the placement of the scarf joints
3. Preparing the scarf joints

Here we go, with pictures...

1. Cutting one end to fit at the stem

After a little testing with some paper-thin wood templates, I found that the angle at the front tip of the chine was almost exactly 60°. Easy enough to cut.

Then, with a little trial and error, I cut the bevel so that the tip of the chine would fit against the stem as best possible.

2. Planning the placement of the scarf joints

Just as with the first lamination, what I have to work with are 4 strips of mahogany approximately 3/8" thick x 2" wide, and a little over 4 feet long. 

The three scarf joints on the first lamination lie between Frame #5-1/2 and Frame #4 (about halfway); between Frame #4 and Frame #2 (again, about halfway), and between Frame #2 and the Transom, approximately 16" forward of the transom. (These locations correspond with zones 7, 6, and 5 in the graphic below.)

My goal with the second lamination is to stagger the locations of the scarf joints, so that the joints on lam 1 will be backed by solid wood on lam 2. In doing so, I need to make sure that the scarf joints of lam 2 do not wind up directly over the frames.

The forward strip of lam 2, fitted & clamped onto lam 1. The 2nd strip is shown loosely in position. The joint between the two will have to be located forward of Frame #5-1/2.

The 2nd strip of lam 2, clamped loosely into place so that it is centered over the scarf joint of lam 1.

The scarf joint between the 2nd strip (shown) and the 3rd strip (not shown) will have to be located slightly aft of Frame #4.

The placements shown above will allow the scarf joint between the 3rd and 4th strips to be located approximately 1 foot aft of Frame #2. The 4th strip will then cover the aft-most scarf joint of lam 1.

3. Preparing the scarf joints

According to the Glen L. Witt's book, Boatbuilding with Plywood, the ideal ratio for a scarf joint is 1:12. I found that this roughly corresponds to a 5° cut. 

So, I made this cut on a scrap of 2x4 to use as something of a "sled" for my table saw:

Not Swiss-watch precision, but it works.

I made the cuts, and then lay the strips one on top of the other, aligned so that I could sand the surfaces for the best possible fit.

With all that done, I clamped all the parts into position to make sure everything will fit correctly.

This view shows the aft end of the 2nd strip, before I had made the 5° scarf cut.

Location of the forward-most scarf joint, just forward of Frame #5-1/2

(slightly closer view)

All the parts clamped into place.

Now, when that order of epoxy gets here, it'll be time to put all this together.

I may actually need more clamps.

Have a happy and safe Memorial Day weekend.